1. Technical Field
The present disclosure relates to an illumination system and, more particularly, to an illumination system having a low energy consumption.
2. Description of Related Art
LEDs have been available since the early 1960's. Compared with the conventional light sources, such as fluorescent lamp, halogen lamp and incandescent lamp, the LEDs have a higher electro-optical conversion efficiency. Thus, nowadays LED usage has been increased in popularity in various applications, particularly, the applications needing large power consumption, in order to reduce operation cost of these applications.
A road lamp is one type of lamps consuming a larger amount of power; thus, it is extremely desirable to replace the typical light source of the road lamp with the LEDs. However, even employing the LEDs as the light source, the road lamp still has a large power consumption since a high luminous flux is required for ensuring sufficient luminosity on the road needing be illuminated by the lamp. Therefore, many attempts are tried to reduce the power consumption of the LED road lamp, such as increasing the electro-optical conversion efficiency of the LEDs, raising brightness of the LEDs, optimizing light pathway in the lamp, and improving electrical circuits connected to the lamp.
Nevertheless, these attempts are difficult to achieve significant effect due to the technologies thereof having been developed for a long time and reached respective bottlenecks. On the other hand, there is a phenomenon ignored in road illumination all the time, that is, the lamp always keeps a constant brightness all over the illumination period thereof, even in the late night where the traffic flow is relatively low. In fact, at the late night there is no need to provide such a high intensity as that at early night to illuminate the road just for few vehicles driving on the road. The lamp would waste a large amount of power to maintain the constant brightness thereof.
What is needed, therefore, is an illumination system which can overcome the above-mentioned disadvantages.